Save Mac screenshots as JPG to shrink file size

macOS saves every screenshot as a PNG — pixel-perfect, but heavy, with a single full-screen grab easily topping several megabytes. Switch the default to JPG and the same shot lands at a fraction of the size. There's one Terminal command for it; here's the command, the undo, and when PNG is still worth keeping.

Change the screenshot format to JPG

macOS reads a single preference for the screenshot file type. Set it to jpg and every screenshot from then on saves as a JPEG:

# Save screenshots as JPG instead of PNG
defaults write com.apple.screencapture type jpg
killall SystemUIServer

# Undo — back to the default PNG
defaults write com.apple.screencapture type png
killall SystemUIServer

The killall SystemUIServer line restarts the process that handles screenshots so the change takes effect immediately — nothing else on your Mac is disturbed. To remove the setting entirely rather than switch it to PNG, run defaults delete com.apple.screencapture type followed by killall SystemUIServer. This works on macOS 13 Ventura, 14 Sonoma, and 15 Sequoia.

Check it worked

Take any screenshot (Shift+Cmd+3 for the whole screen) and look at the file that appears — the name now ends in .jpg instead of .png. Get Info on an old PNG and the new JPG of a similar shot and the size difference is stark: a busy 4 MB PNG often becomes a few hundred kilobytes as a JPG.

There's no System Settings switch for this

Unlike the save location, the file format has no toggle in System Settings or in the Screenshot toolbar's Options menu — the Terminal command above is the built-in route. That's the one thing to know before you go hunting through menus for it.

When PNG is still worth keeping

JPG is lossy: it compresses by discarding detail your eye barely notices on a photo, but on a screenshot that means slightly softened text and fuzz around sharp, high-contrast edges. Weigh it up:

• Choose JPG for screenshots you'll email, upload, or paste into chat — anywhere size matters and a hair of softness doesn't.
• Keep PNG for crisp UI mockups, anything with fine small text you'll zoom into, or images that need a transparent background (JPG can't do transparency).

The same preference accepts other values too — pdf, tiff, heic, and gif — if a particular workflow needs one of those instead. For most people chasing smaller files, jpg is the answer.

Move them off the desktop too

Smaller files still pile up if they all land on the desktop. Point them at a folder with how to change the screenshot save location on Mac.